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Role of Particles in Flame Inhibition by Iron Pentacarbonyl.


pdf icon Role of Particles in Flame Inhibition by Iron Pentacarbonyl. (1001 K)
Rumminger, M. D.; Linteris, G. T.

Halon Options Technical Working Conference. Proceedings. HOTWC 1999. April 27-29, 1999, Albuquerque, NM, 511-521 pp, 1999.

Keywords:

flame extinguishment; chemical inhibition; flame chemistry; halon alternatives

Abstract:

Certain metallic compounds have been found to be substantially more effective flame inhibitors than halogen-containing compounds. In particular, iron pentacarbonyl (Fe(CO)5) was found to be one of the strongest inhibitors--up to two orders of magnitude more effective than CF3Br at reducing the burning velocity of premixed hydrocarbon-air flames. Although Fe(C0)5 is highly toxic, understanding its inhibitory effect could lead to development of effective non-toxic agents. Measurements of Fe(CO)5-inhibited premixed flames have shown that the inhibition varies with the Fe(CO)5 concentration: at low mole fraction the burning velocity is strongly dependent on inhibitor mole fraction, while at high Fe(CO)5 mole fraction the burning velocity is nearly independent of inhibitor mole fraction. A critical part of the research on Fe(CO)5 is to understand iron pentacarbonyl's diminishing effectiveness at high mole fraction in order to avoid similar behavior in future fire suppressants. A plausible but unconfirmed explanation for iron pentacarbonyl's reduced effectiveness under certain conditions is that particles form, thus reducing the gas-phase mole fraction of active inhibiting species. To investigate this possibility, we use laser-light scattering to measure particles in premixed flames with added Fe(CO)5 and determine if the conditions of high particle concentration correspond to the regions of reduced inhibition effect. Alternatively, if there is high particle density for conditions at which Fe(CO)5 has a strong inhibition effect, then the search for halon alternatives could be directed toward chemicals that produce similar condensed-phase compounds.